1. Field of the Invention
The present invention relates generally to a driving device, and more particularly, to a pulse width modulation (PWM) step wave and sine wave driving device in accordance with a predetermined operation mode, for avoiding system breakdown or failure caused by abnormal power supply of the system.
2. The Prior Arts
Many electric products or electronic apparatuses, e.g., transformers, motors, speakers, LED illuminating devices, LED displays, LCDs, or converters, require facilitation of driving devices for regular operation. However, such driving devices are required to have the capability of stably outputting driving signals without being affected by external noise and system power supply variation.
Typically, an electric device, e.g., a motor or a transformer is driven by alternating current (AC) signals, and thus can be driven with a full bridge driving stage constituted of a plurality of power transistors. The gate of each power transistor is controlled by a driver, so that the direction of the current flowing through the electric device alternatively varies. The most often used driving method is known as pulse width modulation (PWM). A conventional PWM employs pulse signals of different widths for achieving a precise control of the power transistor, so as to output the desired AC to the electric device.
Such a conventional technology has certain disadvantages. For example, the driving device is incapable of proactively detecting the variation of the system power supply for dynamically adjusting to achieve optimal driving signals to prevent the electric device from being further affected by the variation of the system power supply. Specifically, when the system power supply is in an abnormal condition. For example, an excessively high or low frequency may cause the driving device failing to output suitable driving signals. In that way, the electric device may fail to operate, or even be permanently damaged, even cause the entire operation system to breakdown. Therefore, it would be very much desired to provide a driving device for generating suitable driving signals in case the system power supply is in an abnormal condition, and maintaining to output stable driving signals against variation of the system power supply.